Release 0.9.6 "Peace" - Bug fixes

This release is mostly bug fixes

Bug fixes
=========

* Evaluate index in `get` and `put` like the HP50G
* Avoid premature simplification during arithmetic operations
* Do not wrap variables after `Copy`, e.g. in `'A+A▶A+A'`
* Return errors for unknown primitives / derivatives in algebraics
* Correctly use `GraphicReslutDisplay` for result stack level
* Ensure pi and e display the same size at 60 digits precision
* Fix bogus exponent truncation in polynomials
* Fix issue in `+` and `-` on vectors with angles, e.g. `[ 3 2 1.7_° ]`
* Fix possible garbage collection memory corruption in `FromVector`

Improvements
============

* units: Make `BaseUnits`, `→Deg`, `→Rad`, `→Grad` and `→πr`  array-wise
* Add `VectorMenu` on first page of `MatrixMenu`
* Do not single-step or debug during plot/integration
* Add routine to render u64 and i64

Signed-off-by: Christophe de Dinechin <christophe@dinechin.org>